Josh, thanks so much. Now, to the shocking results of an abc news/espn exclusive investigation into the death of nfl great junior seau. Doctors revealing their findings for the first time. And it could affect players from the big leagues to pop warner. Abc's jim avila is here with the story. Good morning. Reporter: Good morning. A giant in the game, junior seau is the biggest name in football, linked to brain damage for taking too many hits to the head. Abc news and espn learned exclusively, before his suicide, seau suffered damage to his head. Junior seau, an icon in the 1990s, WHOSE PASSIONATE HITS Made him a dominant figure in the nfl. But after his sudden suicide in 2012, many questioned whether the effect of those hits on the 43-year-old's brain, could have played a role. The head-to-head contact, the collisions, they're out of control. Reporter: Now, seau's family says it has an answer to that question from the national institutes of health. Abc news and espn have learned exclusively, seau's brain showed visible signs of cte, chronic, traumatic encephalopathy, the injury that shrinks and hardens brain tissue like this. And is at the center of today's football safety controversy. I think for us, we just wanted the truth. Reporter: It was seau's family who decided to donate his brain to the nih, in an effort to find out why the man who confronted life on the field and off, shrunk from it in his final living years. Ending it all, detached and alone. He loved the game. But I know that he didn't love the end of his life. Reporter: Do you think this condition, now it's been diagnosed clearly, what role did it have in that? I think it played a huge effect. Just him not being aware of the things he could possibly go through. Reporter: Seau was a respected family man, with four children, and an ex-wife with whom he was close until he shocked them all, by shooting himself in the chest, leaving only this short phone text of love the night before. Just three words. I love you. That was the last we heard. Reporter: For the seaus, football gave them everything. And they believe, now, has taken it all away. They understand its attraction, and all too well its routine danger. I think it's a gamble. Just be extremely aware of what could potentially happen to your life. Reporter: There's a big risk? There's a huge risk. It's not worth it for me to not have a dad. So, to me, it's not worth it. Reporter: None of the seau children play football anymore. And their mother is glad of that. The nfl says it did not intentionally hide the dangers of concussions from players. And is doing everything it can now to protect them.

This transcript has been automatically generated and may not be 100% accurate.

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